The guinea pig (Cavia porcellus) is a favorite friend animal and a research model that is common.
- Intact guinea that is female are “sows” and intact males are “boars”.
- Mature boars have actually distinct scrotal pouches and big testes.
- Male guinea pigs have actually a few sex that is accessory, including big, paired seminal vesicles or vesicular glands, which may be seen erroneously as uterine horns.
- Puberty does occur at more or less 2 months in females and between 2-3 months in males.
- The symphysis that is pubic within the last few times of maternity.
- Separation of this symphysis that is pubic be insufficient in sows bred after 7-8 months of age and dystocia may result in him or her. Other possible factors behind dystocia consist of obesity and large fetal size.
- Sows usually give delivery to 2-4 big, precocial pups. Other rodent types generally speaking have actually big litters.
- Pregnancy toxemia is a cause that is important of mortality in guinea pigs. This problem is frequently observed in primiparous, overweight sows in belated gestation. The prognosis can be guarded. Minimize the danger of maternity toxemia by motivating workout, preventing obesity, and minimizing stress in the sow that is pregnant.
- Unilateral or bilateral ovarian cysts are quite typical, especially in older sows.
- Ovariohysterectomy or ovariectomy is advised to stop the growth of ovarian cysts along with other problems that are reproductive non-breeding friend sows.
Guinea pigs are helpful in reproductive studies simply because they share numerous traits that are reproductive people (Fig 1). 26 Like people, guinea pigs have a very hemochorial placenta, by which maternal bloodstream is available in direct connection with the fetal chorion, in addition to comparable trophoblast intrusion habits and uterine vasculature that is comparable. 20 , 23 , 26 The guinea pig’s gestation duration may also be divided in to trimesters, analogous into the condition that is human. 26 needless to say, some top features of guinea pig reproductive anatomy and physiology are distributed to other users of Order Rodentia, along with other features are unique for this species that is special. This short article product reviews structure and physiology of this guinea pig tract that is reproductive summarizes some clinically significant medical dilemmas.
Figure 1.Guinea pigs (Cavia porcellus) are helpful in several studies that are reproductive.
Intact guinea that is male, or “boars”, enter puberty between 70-90 times, nevertheless men start to show intimate behavior, such as for example mounting, at four weeks of age. 9 , 17 , 23 At 2 months, boars start to ejaculate while mounting. 23 Expression of sexual behavior and development that is physical notably suppressed in the event that boar is housed using its mom and/or siblings. 11
Boars are usually bigger than females, with both sexes having a pair that is single of mammae. 5 Mature boars have large, paired testes, that are found on either region of the perineum in distinct, superficial scrotal sacs (Fig 2). 5 , 9 , 23 The testicles are frequently completely descended in to the scrotum by 81 days. 2 In the event that testes never have descended by 4 months of age, the guinea pig should be thought about cryptorchid. 9 The inguinal canals remain available for a lifetime. 9 , 19 to avoid herniation post-castration, numerous clinicians use a closed strategy or even a modified available strategy, where in fact the tunica is roofed when you look at the suture which is used to connect from the spermatic cable and vessels. 32
Figure 2.Gross image for the testicle (arrow) in an adult boar (Cavia porcellus). The epididymis lies across the surface that is dorsolateral of testis. The end of this epididymis provides rise to your ductus deferens. Credit: Drury Reavill, DVM, DABVP (Avian Training), DACVP. Click image to expand.
Clinical Suggestion: Although big, paired testes are unmistakeable in mature boars, sex identification may be challenging in young pups. In the event that testicles aren’t apparent, sexing are facilitated by putting pressure that is gentle the bottom for the prepuce to partially extrude your penis. 23
The S-shaped penis comprises of the human anatomy and glans. Guinea pigs have a penis that is os which will be discovered inside the dorsal area associated with the entire amount of the glans. 9 , 19 Like many hystricomorph rodents, your penis comes with moment, saw-toothed spurs that are white dorsolaterally in 2 synchronous lines through the urethral orifice to your glans. There’s also a sac that is intromittent the ventral surface associated with glans penis. 9 During erection, the sac everts and two styles that are horny. 5 , 9 , 23 the event of those 3-5 mm projections that are long unknown. 9
Male reproductive glands include the seminal vesicles (vesicular glands), coagulating glands, bulbourethral glands, while the prostate (Fig 3). 5 , 27 A rudimentary preputial gland may additionally be contained in the boar. 9
Figure 3. Reproductive anatomy regarding the guinea pig (Cavia porcellus) boar. (A) seminal vesicle (B) testis C) vas deferens (D) anterior prostate gland or coagulating gland (E) urinary bladder (F) Cowper’s or bulbourethral gland (G) urethra (H) penis (we) epididymis. Photo credit: Drs. Craig Franklin and Cindy Besch-Williford. Click image to expand.
- The big, clear, smooth vesicles that are seminal the biggest reproductive glands of the boar, calculating as much as 100 mm in total and 6-9 mm in diameter. These long, coiled, paired sacs that are blind ventral to the ureters and enter the urethra by a set of ducts instantly caudodorsal towards the ductus deferens. 9 , 19 , 23 , 27
Clinical Tip: The big, paired vesicles that are seminal be seen erroneously as uterine horns.
Each locks follicle regarding the guinea pig is related to an androgen-dependent sebaceous gland. These glands are numerous across the relative as well as may also be discovered round the rectum, where they truly are called the caudal gland or “grease gland”. 9 , 23 The caudal gland is much more developed into the boar and it is utilized for fragrance marking (Fig 4). Boars often rub or push their rump against a area, while the secretions deposited act as a sexual attractant and to mark territory. 9 , 23
Figure 4.Caudal gland (big arrow) and perineum (little arrow) in a male guinea pig (Cavia porcellus). Supply: Uwe Gille via Wikimedia Commons. Click image to expand.
Puberty does occur around 2 months of age into the guinea that is female or “sow”. 23 Peak reproduction is seen between 3-4 to 20 months and reproduction may carry on until 4-5 years old. 19 , 23 Guinea pigs are seasonally polyestrous and breed year-round in captivity. 9 , 23 Sows are spontaneous ovulators, having an estrous period between 15-17 times (range 13-21 times). 19 Sows display distinct signs and symptoms of proestrus and estrus. During proestrus, sows are more active, chasing cage mates around, swaying their hindquarters, and creating a definite guttural noise. Estrus lasts 6-11 hours, and in this right time the sow shows lordosis, curvature of this back with elevated sides, along with vulvar dilation. 23
The sow possesses a pair that is single of mammary glands with an individual set of inguinal mammary nipples (Fig 5), but supernumerary nipples are normal. 9 , 19 , 22 compared to the boar, the sow’s nipples are much much much longer and much more prominent. 9
Figure 5.Both male and female guinea pigs (Cavia porcellus) have just one couple of inguinal mammary glands. Supply: Drury Reavill, DVM, DABVP (Avian Training), DACVP. Click image to expand.
Sows have paired ovaries and a bicornuate womb, composed of paired uterine horns, an uterine that is short, and just one os cervix (Fig 6, Fig 7). 5 , 9 , 23
Figure 6.View of just one uterine horn (arrow) in mature guinea pig (Cavia porcellus). Source: Drury Reavill, DVM, DABVP (Avian training), DACVP Click image to enlarge.
Figure 7.Gross view regarding the uterine horns (small arrows) and the body (big arrow) in a guinea pig (Cavia porcellus). Supply: Drury Reavill, DVM, DABVP (Avian Training), DACVP. Click image to expand.
During anestrus and pregnancy, the genital opening in hystricomorph rodents is sealed having an epithelial membrane called the genital closing membrane layer. The membrane starts at estrus, Day 26 or 27 of gestation, and also at parturition in lots of pets. 19 , 22 , 23 , 29 The sow features a depression that is y-shaped perineal cells. The opening that is vulvar at the intersection of this branches while the anal area is situated at the root of the Y (Fig 8). 23
Figure 8.Y-shaped despair when you look at the perineum of a guinea pig sow (Cavia porcellus), illustrating the vulva (white arrow) as well as the anal area (yellow arrow). Supply: Dorcas O’Rourke, DVM, MS friend finder, DACLAM. Click image to expand.
Each time a female that is receptive introduced, the boar starts to purr and sway his posterior back and forth, while circling, and often brushing from the sow and on occasion even spraying urine during the sow. In the event that feminine is unreceptive, aggressive male behavior can be seen such as for instance barbering hair regarding the female’s throat. 19 a female that is receptive let the male to sniff and lick her anogenital region. 6 , 11 , 19 She assumes the lordosis place and enables a man to mount her. Whether ejaculation happens or perhaps not, a man shall perform vaginal grooming by dragging their perineum over the cage flooring. Meanwhile the doubles that are female and makes use of her lips to groom her genitals. 19 Mating often happens at night. 8
Copulation is verified by the existence of a strong, rubbery deposit inside the vagina called the copulatory or genital plug, consists of a solid mass of ejaculatory fluid. 23 there are many theories in the purpose of the copulatory plug in rodents, including semen storage space, avoidance of semen leakage, advertising of sperm transportation, and/or to stop later on fertilization by other males. 23 The copulatory plug falls out a long time after mating. 23
The normal guinea pig maternity persists 68 times, with a reported array of 59-72 times. 9 , 19 , 23 These times differ with stress, parity, and size that is litter. 23 typical litter size is 2-4 pups with a selection of 1-13 pups. 23 clear abdominal distension just isn’t observed until belated gestation. 8